Pholcus is a distributed, high-concurrency, and powerful web crawler software written in the Go programming language. It is primarily designed to scrape data from websites, both static and dynamic. However, it is important to understand the distinction between static and dynamic websites in the context of web scraping.
Static websites are those that serve the same content to all users from the server's filesystem. The content does not change unless it is updated by the webmaster. Such websites can be easily scraped because the data is embedded directly within the HTML served to the client.
Dynamic websites, on the other hand, often load content dynamically using JavaScript, which may not be present when the initial HTML is loaded. This content is typically fetched using additional HTTP requests that the browser makes after loading the initial HTML, often in response to user actions or as part of the page's lifecycle.
Pholcus supports scraping dynamic content, but it may require additional setup compared to scraping a static website. For dynamic websites where content is loaded through JavaScript, a crawler must be capable of executing JavaScript code just like a browser does. Pholcus, being a sophisticated crawler, can handle such cases using a headless browser or similar techniques to execute JavaScript and fetch the content once it has been loaded.
Here's an example of how you might use Pholcus for scraping static content, given that Pholcus has a slightly different approach to scraping compared to other tools:
package main
import (
"github.com/henrylee2cn/pholcus/exec"
_ "github.com/henrylee2cn/pholcus_lib" // This is where spiders are registered.
// _ "github.com/henrylee2cn/pholcus_lib_pte" // If you need, import the plugins.
"github.com/henrylee2cn/pholcus/web"
)
func main() {
// To run Pholcus as a web application:
web.Run()
// Or to run Pholcus in command line mode (which does not start the web interface):
// exec.DefaultRun("web")
}
For dynamic websites, you would have to make sure that Pholcus is configured to execute the necessary JavaScript. This might involve using a headless browser in conjunction with Pholcus or leveraging any built-in JavaScript execution features it provides.
As for JavaScript and Python, while they are popular languages for web scraping, Pholcus is a Go-based framework, so you would need to use Go to work with it. If you need to scrape a dynamic website using JavaScript or Python, you would typically use tools like Puppeteer (for JavaScript) or Selenium with a headless browser (for Python).
Here's a simple example using Puppeteer in JavaScript to scrape a dynamic website:
const puppeteer = require('puppeteer');
(async () => {
const browser = await puppeteer.launch();
const page = await browser.newPage();
await page.goto('https://example.com');
// Wait for the required element to be loaded
await page.waitForSelector('selector-of-dynamic-content');
// Extract the content of the element
const dynamicContent = await page.evaluate(() => {
return document.querySelector('selector-of-dynamic-content').innerHTML;
});
console.log(dynamicContent);
await browser.close();
})();
And here's an example using Selenium with Python:
from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
driver = webdriver.Chrome()
driver.get("https://example.com")
try:
# Wait for the required element to be loaded
element = WebDriverWait(driver, 10).until(
EC.presence_of_element_located((By.CSS_SELECTOR, "selector-of-dynamic-content"))
)
# Get the content of the element
dynamicContent = element.get_attribute('innerHTML')
print(dynamicContent)
finally:
driver.quit()
Remember to replace https://example.com and selector-of-dynamic-content with the actual URL and the appropriate CSS selector for the content you are trying to scrape.
